Most commercial spammers don’t bother with user names or personal details, just the usual alpha-numeric rubbish such as ‘qwerty123’ and location as ‘1’ etc.
If it was possible to set up something to identify such user names as suspect, the next step would be an auto-response requiring them to submit their first ten posts by PM to a mod PM address, which is accessible to any mod. Most spammers probably couldn’t be bothered.
If such a system picked up genuine new members then mods could let them post.
I don’t know if vBulletin can support that or if something else can do it, but it would get rid of about 95% of the remaining spammers coming through the improved filter.